1. Field of the Invention
The present invention relates in general to a method of molding a foamed plastic article, and more particularly to a method of molding a skin-covered foamed plastic article, which generally comprises by steps placing a bag-shaped skin member in a mold in a manner to intimately cover the wall of the cavity of the mold, pouring a liquid material of foamed plastic into the bag-shaped skin member in the mold, curing the material and removing a product, viz., a skin-covered foamed plastic article from the mold upon hardening of the material.
2. Description of the Prior art
In order to clarify the task of the present invention, one conventional method of molding a skin-covered foamed plastic article will be described with reference to FIGS. 3, 4 and 5 of the accompanying drawings, which method is disclosed in Japanese Patent Second Provisional Publication No. 60-18434.
Referring to FIG. 3, there is shown a seat 100 of a motor vehicle, which includes a seat cushion (no numeral) and a seatback 101 which are produced by the conventional molding method. The seatback 101 includes a foamed plastic portion 104 serving as a cushion means, a skin member 103 intimately covering the foamed plastic portion 104 and a metal frame 105 serving as a structural base of the seatback 101. As is seen from FIG. 4, the skin member 103 is shaped like a bag consisting of stitched two parts, one being a front part 103A and the other being a side part 103B. These two parts 103A and 103B have respective inwardly projected peripheral portions stitched up. The stitched portions are denoted by reference "N", which, as is seen from FIG. 3, extend around the side walls of the seatback 101. As is best shown in FIG. 5, each part 103A or 103B of the skin member 103 is of a two-layered skin which comprises an outer skin "O" of cloth and an inner skin "I" of wadding.
The seatback 101 having the above-mentioned construction is produced by employing the following producing steps.
First, a bag-shaped skin member 103 is put into a cavity of the mold with its mouth portion directed upward. Then, a liquid material of foamed polyurethane is poured into the bag-shaped skin member 103 in the mold. Then, a lid is put on the mold to close the cavity of the mold. During curing, the material foams and thus presses the skin member 103 on the inner wall of the mold. After the material is cured and hardened to a certain level, a skin-covered foamed polyurethane article, viz., a skin-covered seatback pad, is removed from the mold. Then, the seatback pad is fixed to the metal frame 105 to constitute the seatback 101.
However, in the conventional method as described hereinabove, it is very difficult to provide the stitched portions "N" with a satisfied external appearance having suitable waves. That is, when the urethane material overfoams for some reason, the front and side parts 103A and 103B of the skin member 103 are overly drawn by each other thereby forming a simple and flat outer looking at the stitched portions "N". While, when the foaming of the urethane material is poor, unsightly creases are numerously formed on the stitched portions "N".